Effect of Side Chain Rigidity on the Elasticity of Comb Copolymer Cylindrical Brushes:  A Monte Carlo Simulation Study

Abstract

We report the results of a Monte Carlo simulation study of isolated comb copolymer cylindrical brushes. The conformational characteristics of molecules consisting of a flexible backbone densely grafted with side chains strongly depend on the rigidity of the side chains, which is exemplified by using both fully flexible and totally rigid side chains. The short length scale fluctuations of the backbone are not affected by the presence of rigid rod side chains, whereas flexible side chains induce local stretching of the backbone. However, at the large length scale, the persistence length λ of the cylindrical brush is considerably larger for rigid rod side chains than for flexible side chains. Moreover, for rigid side chains the ratio between the persistence length λ and the diameter D of the brush increases approximately linearly as a function of the rod length L, thus supporting the possibility of lyotropic behavior. In contrast to this, in the case of flexible side chains, λ/D is approximately independent of the side chain length M.

Synthesis and Solubility of (Mono-) End-Functionalized Poly(2-hydroxyethyl methacrylate-g-ethylene glycol) Graft Copolymers with Varying Macromolecular Architectures

“…The cloud point temperature was taken at 50% of the starting current signal in the raw data plots of part a. The dashed line is an empirical best fit curve to the data to guide the eye (y ) A -(x -B) 2 , A ) 271254, B ) 520, R 2 ) 0.85).…”

Ring comb copolymer brushes

“…These motions have been described in detail in our previous publications. 22,[24][25][26] For the rigid side chains only one type of side chain move was used. A randomly chosen side chain is given a new orientation, which is chosen isotropically.…”

“…The stiffer the side chains, the larger the persistence length of the comb copolymer molecule. 26 Hence, rigid rod side chains turn out to be most effective in this respect. However, in the case of ring comb copolymers with rigid rod side chains, overlap between side chains from opposite sides of the ring backbone is almost inevitable unless extremely long backbones are used.…”

“…6,13 In general, the presence of a large number of side chains results in severe stiffening of the structure leading to cylindrical comb copolymer brushes ͑or molecular bottle-brushes͒. These molecules have also been investigated theoretically [14][15][16][17][18] and with computer simulations [19][20][21][22][23][24][25][26][27][28][29][30] in some detail. Our studies focused mainly on the persistence length as a measure of the stiffness.…”

“…Computer simulations have been used extensively by Saariaho et al 22,[24][25][26][27] to address the behavior of /D as a function of side chain length for various cases. The influence of the stiffness of the side chains on this ratio was considered in some detail and interesting differences were found between the two cases of completely flexible and rigid rod side chains.…”